advice on a system

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You might want to consider putting in an aftermarket head unit, although it's not necessary it will usually give you much better sound quality overall.  As for the speakers, I think it'd be possible to make the bostons fit but the 6x9s are gonna be tough to squeeze in there, and even then you'd be looking at a lot of cutting your car apart.

I'd have to look into the sizing and speaker locations a lil more before i could give you a definite answer or suggestion regarding the speakers. So bear with me...

My brother happens to have a 95 Z28 with the same setup of speakers (6.5's in the doors and behind the seats).  It would take a lot work to get 6.x9's to sit properly in that type of car.   So my  advice would  be to use a speaker size to match the factory as close as possible.  For example my brother is running a Pioneer Deh-8500 to Pioneer Separates (don't know which model) the 6.5 mid bass in his doors and Pioneer 2 ways in the rear.   And MTX thunder form 10 inch in the factory sub location (the car previously had the factory bose system in it-which was a pain to remove). running off the sup output of the head unit.    That's just my opinion.  But You definetly have come to the right place to get info on car audio.   

Hey guys, It's me again. I wasn't actaully thinking about using my speakers in the stock mounts. I was actually think about getting a high power head unit w/ two output RCA sets. I would connect the stock kickpanel speakers to two of the cannels and then split the other two channels of the unit to the rear stock speakers and my 3 1/2's which I want to mount in the dash, then using the stuff I already had, I build a box to custom fit the hatch of my car and power it with the 200w amp. Last, I was thinking about using the other output to connect to the 600w amp and then to the two 6x9's in boxes which will sit where the sub box is. With this system all I have to buy is a head unit. I don't know which one to buy though.